PROJECT SUMMARY High prevalence of obesity contributes to stagnant mortality rates, increased health care spending, decreased employment, and lower wages. Current gold standard treatments are costly and burdensome, limiting accessibility to the majority of the public and having little effect on this public health crisis. Many attempts have been made to improve the delivery of the successful Diabetes Prevention Program (DPP), shown to produce an average of 6.5kg weight loss over 6 months. However, research to date has lacked a systematic optimization of the DPP treatment package, resulting in packages that have essential parts missing, continue to be burdensome for the patient, or do not produce enough weight loss. The proposed work represents the next step in an efficient, systematic process to identify active treatment components with the goal of assembling a treatment package that can produce sufficient weight loss at a reduced cost and burden. Our prior trial, Opt-IN, was a highly efficient, fully powered full factorial randomized trial designed to test main effects and interactions of additional treatment components (e.g., text messages, meal replacements), when added to a minimal intervention of self-monitoring, psychoeducation, diet and physical activity goals, and biweekly coaching calls. The results supported that significant weight loss could be attained from a minimal level of intervention with no additional components. One notable finding demonstrated that 24 coaching sessions was no better than receiving 12 sessions, significantly reducing potential cost of an intervention. While the Opt-IN trial was designed to test contribution of components, a full head-to-head randomized controlled trial will need to be conducted between the newly optimized intervention (EVO: Elements Vital to treat Obesity) and the current gold standard DPP. Furthermore, full economic analyses that use concurrent clinical trial data from weight loss treatments is lacking, and as such, we intend to do so to inform future dissemination, implementation, and/or further optimization of treatments. Aim 1 is to test whether weight loss from baseline to 6 months achieved by EVO is non-inferior to DPP. Aim 2 will focus on conducting a full economic evaluation consistent with current guidelines. Finally, exploratory aims will investigate weight loss maintenance at 12 months as well as change in self-regulation, moderators (i.e., Age, Sex, Socioeconomic status) and mediators (i.e., self-monitoring adherence, self-efficacy) of treatment effects.